Field of the Disclosure
The present disclosure relates generally to media sheet finishing apparatuses, and, more particularly, to a hole punch system for punching holes through a media sheet, and methods of utilizing the same.
Description of the Related Art
Sheet processing devices are used to perform further processing, such as stapling and punching, on media sheets that have undergone image formation. In recent years, imaging devices have been incorporated with finishers, which include hole punch and/or stapler mechanisms, post stage after image formation in order to apply finishing to imaged media sheets.
One known type of sheet punch mechanism creates holes in a sheet using a rotary punch. With this type of mechanism, holes are punched in the media sheet by advancing the media sheet along a media path while at the same time rotating a punch and a die in the same direction as the media sheet feed direction. Holes are punched through the sheet when both punch and die meet at a common point (the punch point) along the media path while the advanced media sheet is between the punch and die. Accordingly, holes can be punched through the media sheet without stopping the media sheet, allowing higher throughput.
In some existing rotary punch type mechanisms, stepper motors are used as punch motors to rotate both the punch and die because of the simple control configuration of stepper motors. More particularly, due to a stepper motor's nature of rotation by fractional increments or steps, it can be easily driven using open-loop control to provide positioning of the punch and die without requiring any feedback signal. That is, by knowing the speed of the media sheet and the expected time that a desired punch location on the media sheet will reach the punch point within the punch system, one can easily command the stepper motor to run a number of steps at a particular rotational speed that would cause the punch and die to also engage the punch point at the expected time of arrival of the punch location at the punch point.
Unfortunately, open-loop stepper motor control has several drawbacks such as when used in hole punch systems. In terms of cost, systems utilizing stepper motors are generally expensive. In terms of reliability, hole punch systems utilizing open-loop stepper motor control cannot compensate for any disturbance of or correct any error in the system. For example, punch systems have varying loads (e.g., different media types, speeds, etc.) and position and/or speed control of the stepper motor can be lost if a specific media type slows the rotational speed of the rotary punch from what is being commanded. Since open-loop motor control does not use sensors to determine actual speed or rotational position, the system cannot determine errors in punch speed and position and, thus, cannot perform compensations if any form of disturbance occurs. This often results in drift and incorrect hole positions which compromises hole quality. In order to ensure that the stepper motor would not stall over the range of the expected load, a torque margin is necessary which in turn results to more power consumption by the system. In another example, stepper motors operate at relatively low speeds and, typically, need to be parked at a home position occasionally (or after every punch) to set up the punch properly for the next hole. This prevents hole punching at high process speeds and affects flexibility in hole placement along the edge of the media for varying media sheet sizes. Moreover, if there are changes in the operating parameters of the imaging system, stepper motors may need to be re-qualified to ensure reliable operation with the new operating parameters.
It would be desirable to have a cost effective and reliable hole punch system that avoids the aforementioned drawbacks.